The farthest Karma has ever "fallen" was when she slid from my stomach onto the bed I was laying onI have never put her around my neck. It just doesn't seem safe when she's only around 2 feet long. Maybe when she's older and bigger I will...but I personally like handling a snake with my hands. I've actually managed to do some minor cleaning with Karma curled up on my hand
I guess it's whatever both you and your snake are comfortable with